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Superficial Back Arm Line The Arm Lines are named for how they present at the armpit level—two in front of the axillary space, two behind. 3 Superficial front Arm Line with the arm and hand's many talents, the shoulder has to slide all over the place, making it more vulnerable to both injury and misalignment. THE ARM LINES The complexity of the myofascial structures along the arm is mind- boggling. The arms have to control the finest instrument the world has ever known—the human hand—at one end, and are anchored into the head, neck, upper spine, ribs, low back, hip, sacrum, and even arguably the femurs at their other end. Let us make some sense of this by organizing the "myofascialature" (I made that up, don't repeat it to anyone with a degree) into a series of connected lines. To qualify, these lines must 1) start at the axial skeleton and go all the way to the fingers, and 2) involve conjoined fascial fibers running in a fairly straight direction. Using those rules, one can divide the arm's soft tissues into four of these lines. We name the Arm Lines for how they are arranged in the armpit (Image 3). The pectoralis major is part of the Superficial Front Arm Line (SFAL) (Image 4A). The pectoralis minor and subclavius, and the fascia that surrounds them, are part of the Deep Front Arm Line (DFAL). In the back, the trapezius and deltoid form the beginning of the Superficial Back Arm Line (SBAL) (Image 4B). Beneath these are the rhomboids and levator scapulae leading to the rotator cuff of the Deep Back Arm Line (DBAL). These lines terminate in the four corners of the hand—the palm, thumb, back of the hand, and little finger respectively. Because the intricate anatomy is 2 The arm and leg are similarly designed in a 1, 2, 3, 4, 5 arrangement of bones, and the muscles are easily comparable as well. The arm tilts this design toward extra mobility, while the leg tends toward greater stability. beyond the scope of a short article, you can follow the individual structures in each line by following the charts in Image 4. For simplicity, you can best visualize the four Arm Lines as the four aspects of a bird's wing. Lean forward and stick your arms out like a kid playing airplane: the SFAL is the bottom of your wing from pectorals to palm; the SBAL is the top of your wing from trapezius Deep front Arm Line Deep Back Arm Line A 4 B The four Arm Lines go from the axial skeleton to the four corners of the hand. Celebrate ABMP's 25th anniversary and you may win a refund on your membership. ABMP.com. 99